The chicken was used as a model to study various aspects of glucose metabolism. Glucose replacement rates were very high compared to mammals. Replacement rates were similar in chickens fasted 24 or 72 hours. Glucose metabolism was also investigated in dogs fed various diets. Dogs fed carbohydrate-containing diets exhibited a higher rate of glucose utilization than dogs fed the carbohydrate-free diets. Fasting the dogs for 48 hours reduced the glucose replacement rate in dogs fed the carbohydrate-containing diets but did not influence the rate of glucose utilization in dogs fed the carbohydrate-free diets.